Imagine that you have an interface with two principal panes: a map and a timeline. We want to enable our user to be able to select a job displayed on the map (for instance, "repair washing machine at a location") and drag it to the timeline thereby turning it into an event ("do repair at a given time") whose duration might be represented by a rectangle.
Because the drag operation in effect "converts" one visual object into another as it happens, I think that the user might be confused by the transition.
Of course I plan to run some user tests, but I just wanted to ask whether others consider this to be a legitimate concern and, if so, whether anyone can point me to good solutions to this problem?